Comment 5 for bug 1755587

This is a somewhat strange bug at first glance, because in the MAAS data model, subnets are not directly associated with fabrics. They are associated with VLANs, and VLANs are on a specific fabric. In other words, you cannot actually change the fabric of a subnet. You can only change the VLAN of a subnet, and the new fabric is implied.

That said, I wonder if changing the fabric doesn't automatically update the VLAN drop-down. (When you change the fabric, the VLAN drop-down should change its filter to show the available VLANs on the new fabric.)

Can you test to see if clicking on the VLAN drop-down and choosing the correct VLAN (even if it's already selected) is a workaround? I'm guessing that when you update the fabric, if there is only one VLAN in the new fabric, it is not automatically selected in the VLAN drop-down (the old VLAN, which would no longer be available, but may have the same 'untagged' label, might remain selected).